NANOSPEC - Advanced near-field optical nanospectroscopy and novel applications in material sciences and nanophotonics

The development of novel materials and photonic devices requires nanoscale microscopy for mapping local material properties and confined light fields. Conventional far-field infrared (IR) and terahertz (THz) microscopy and spectroscopy cannot be applied for this task due to its diffraction limited spatial resolution. Scattering-type near-field optical microscopy (s-SNOM) and nanoscale Fourier transform infrared (nano-FTIR) spectroscopy can overcome this drawback as they enable IR and THz imaging of material properties and electromagnetic field distributions with nanoscale spatial resolution. Within this project we want to continue our successful development of s-SNOM and nano-FTIR in order to further establish it as a unique platform for fundamental and applied research in widely different fields. Specifically, we want to establish correlative and simultaneous nano-FTIR, tip-enhanced Raman and photoluminescence spectroscopy (TERS and TEPL). In parallel, we want to apply s-SNOM and nano-FTIR for studying the nanoscale chemical composition of industrially relevant polymer samples and local conductivity of novel organic conductors, as well as for exploring phonon polaritons and vibrational strong coupling in van der Waals (2D) materials. The project is thus divided into three main objectives:

1. Advanced near-field spectroscopy instrumentation
We recently implemented a Raman spectrometer into our IR s-SNOM and demonstrated that TERS can be performed with this instrument. We now want to further develop the setup to allow for both correlative and simultaneous Raman, IR and PL nanoimaging. We also want to develop a background suppression technique for TERS, which will be based on Fourier transform spectroscopy of the Raman scattering and signal demodulation analogue to nano-FTIR spectroscopy. Note that so far a large far-field background signal generally challenges typical TERS experiments, particularly when crowded real-world samples are imaged.

2. Application of s-SNOM, nano-FTIR and TERS for materials characterization We will continue our study of gas separation polymer membranes aiming to clarify the correlation between fabrication process, chemical nanostructure and gas filtration performance. We also want to apply our IR and THz s-SNOMs for nanoscale mapping of conductivity (and related properties) of conducting polymers, which are key building blocks for future organic electronics. Finally, we want to study single photon emitters (SPEs, essential building blocks for future quantum technologies) in h-BN by correlated Raman, PL and IR nanospectroscopy, particularly in the presence of strain.

3. Exploring polaritons in van der Waals (2D) materials
Phonon polaritons in exfoliated h-BN have application potential for molecular vibrational sensing or for enhancing the output signal of graphene-based infrared photodetectors. For practical applications, however, large-scale h-BN layers are needed, to allow for efficient and cost-effective device fabrication. We thus want to employ near- and far-field infrared spectroscopy to explore the properties of phonon polaritons in CVD grown h-BN layers and nanoresonators to be made out of them. Additionally, we will explore vibrational strong coupling (VSC) between single phonon polariton nanoresonators and molecular vibrations to explore VSC on the smallest level of mode confinement and amount of molecules that has been ever achieved.

This project is funded by PID2021-123949OB-I00/MCIN/ AEI /10.13039/501100011033/ y por FEDER Una manera de hacer Europa